1. Field of the Invention
The present invention relates to apparatus for transmitting torque from a driving member to a driven member, more particularly to apparatus for connecting a rotatable device such as a hub to a rotatable shaft such as a motor shaft, and most particularly to a torque coupler wherein axially-exerted hydraulic pressure on opposed outer-ring conical coupler elements causes radial deformation and compression via a doubly conical inner ring with sufficient force that the shaft is gripped by the inner ring, permitting torque to be transmitted between hub and shaft.
2. Description of the Related Art
Friction couplings which rely on radial deformation of an axially-tapered ring for gripping a shaft are known in the art. For example, U.S. Pat. No. 3,569,943 issued Aug. 3, 1971 to Krauss discloses such a coupling wherein an outer ring having a conical inner bore is drawn by a plurality of screws along the mating conical outer surface of an inner ring disposed on a shaft to compress the inner ring against the shaft. Because the screws must be tightened individually, the clamping force exerted on the shaft is applied incrementally at different locations and therefore may not be uniformly distributed when the clamp is fully tightened. Further, it may be necessary to make use of inconveniently strong forces for tightening of the screws. Further, threads can degrade with repeated use, and if one screw jams then the entire assembly may be ruined. Such thread problems can be even more severe when an application requires the use of stainless steel coupler components.
U.S. Pat. No. 4,407,603 issued Oct. 4, 1983 to Lundgren discloses a similar design having a saw-tooth contour which can be formed either by a number of coaxial conical taper portions or by a helical ramp in the inner ring and a mating helical ramp in the outer ring. Again, the inner and outer rings are driven axially of each other by a plurality of screws.
A hydraulically-activated friction clamp is disclosed in U.S. Pat. No. 5,672,026 issued Sep. 30, 1997 to Disborg. The disclosed clamp comprises essentially two opposing clamps having saw-tooth helical mating means like those of Lundgren, the outer rings of the two clamps defining an annular piston and an annular cylinder and being driven apart axially by pressurized hydraulic fluid introduced therebetween. The helical mating means of each of the outer rings mates with a like helical outer surface on a radially-deformable inner ring for gripping a shaft, the outer rings being threaded by their helical surfaces onto the inner ring from opposite axial ends thereof prior to installation of the clamp onto a shaft. The length of the hydraulic stroke of the outer rings is limited to the width of the helical flights (the apparent axial length of each saw-tooth) so that the radial clamping action of the clamp is limited to the radial rise of the helix (the apparent radial height of each saw-tooth). A greater length of radial motion cannot be provided by the screw-mating means of the prior art.
Thus there is a need for a friction coupling wherein a radially-deformable inner member having a conical outer surface is readily insertable into hydraulically-displaceable outer rings without resort to screw means for insertion.
It is a principal object of the invention to provide an improved hub-to-shaft frictional coupling which meets the above objective.
It is a further object of the invention to provide an improved hub-to-shaft coupling having mechanical means for indicating visually that the coupling has been actuated to a desired extent.
It is a still further object of the invention to provide an improved hub-to-shaft coupling having first screw means for positively locking the coupling mechanically in an actuated configuration, permitting removal of hydraulic pressure, and second screw means for positively returning the coupling from an actuated configuration to a relaxed configuration.
It is a still further object of the invention to provide an improved hub-to-shaft coupling having removable means for hydraulic actuation of the coupling.
It is a still further object of the invention to provide an improved hub-to-shaft coupling wherein a central stop on the inner ring assures symmetrical retraction of the outer rings without binding during release of the coupling.